MOLECULAR POLYMORPHISM OF THE LYME-DISEASE AGENT BORRELIA-GARINII IN NORTHERN EUROPE IS INFLUENCED BY A NOVEL ENZOOTIC BORRELIA FOCUS IN THE NORTH-ATLANTIC

Lyme disease Borrelia species are distributed in temperate areas of No rth America and Eurasia. To elucidate the distribution of borreliae in subarctic regions, strains isolated from Ixodes ricinus and Ixodes ur iae ticks found on islands in the northern Atlantic and Baltic Sea wer e molecularly characterized. All isolates were verified as Borrelia ga rinii by 16S rRNA gene analysis and immunoblotting with monoclonal ant ibodies specific for the outer surface proteins A and C. Three ribotyp es (RTs) of B. garinii were delineated. I. ricinus complex-associated RT1 was phenotypically most heterogeneous. Two newly identified riboty pes were shared by different tick species and conformed to two establi shed OspA serotypes. RT2 was restricted to the islands in the northern Baltic Sea, whereas RT3 was recovered also from ticks found in the No rth Atlantic. In conclusion, molecular polymorphism of the studied bor relia isolates suggests a complex enzootic potential of B. garinii in northern Europe and implies a novel, seabird tick I. uriae-associated enzootic focus of Lyme disease borreliae in the North Atlantic.